Inflorescence - Peduncle

[Thomas G. Lammers]

At 07:49 AM 12/6/2004, Richard Jensen wrote:

>Seems to me it matters a lot.  Not all stems develop into inflorescences.

Well, fair enough.  But the point remains, it *is* a stem, not a root or
leaf, and not something sui generis.

>In some inflorescences the peduncle is part of a very well defined unit,
>e.g., the catkins of Quercus.  However, in other cases there is what
>appears to be a gradual transition from stem to peduncle, e,g, in Solidago
>caesia

But does that reflect some biological reality or just human
perception?   Substantively, the only hard and fast difference I see
between the two is the presence of (I assume) an abscission layer that
allows the oak catkin to be "jettisoned" from the branch.  Otherwise, both
are stems bearing leaves and flowers in their axils.

>the flowers are produced in axillary and terminal clusters - are the
>structures subtending these leaves or floral bracts?  Is there a clear
>demarcation between inflorescence and non-inflorescence?

On a practical level, I get the same thing in many Lobelia spp.  A plant at
one stage of development has "solitary axillary flowers" and a month later
has a "terminal raceme."  Seems very different, but isn't.

>I see it as a question of importance in that we speak of the inflorescence
>as an "organ" and if we are to consider it a distinct part of the plant,
>then we need to be able to clearly identify exactly what constitutes the
>inflorescence.

I prefer to keep it loose -- "a collection of flowers" -- and then deal
with specifics of the stems, leaves, and flowers making it up.
Thomas G. Lammers, Ph.D.

Assistant Professor and Curator of the Herbarium (OSH)
Department of Biology and Microbiology
University of Wisconsin Oshkosh
Oshkosh, Wisconsin 54901-8640 USA

e-mail:       lammers at uwosh.edu
phone:      920-424-1002
fax:           920-424-1101

Plant systematics; classification, nomenclature, evolution, and
biogeography of the Campanulaceae s. lat.

Webpages:
http://www.uwosh.edu/departments/biology/Lammers.htm
http://www.uwosh.edu/departments/biology/herbarium/herbarium.html
http://www.geocities.com/TheTropics/Resort/7156/lammers.html
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